Planning Radiation Treatment

For every radiation oncologist, the final treatment strategy is a personally designed plan of attack. Just as surgeons think about how they will approach an operation, radiation oncologists synthesize a great deal of information to come up with the best therapeutic regimen.

Radiation therapy begins with a simulation. During this phase, the oncologist uses techniques of fluoroscopy and CT scanning to localize the particular malignant area of interest. You analyze its relationship to normal and sensitive tissue structures so that they may be protected. Because tissues in the body all have a limit to the lifetime dose of radiation they can safely receive, treatment plans must always take into account this factor. This is where diagnostic imaging, pathology, and indeed the surgeon's narrative, come into play. Radiation oncologists incorporate all of these variables as they come up with a treatment plan.

Because radiation oncologists expose the body to radiation (a foreign sub stance), the goal of therapy is to optimize the beam arrangement so that the prescribed dose reaches the tumor while minimizing exposure to normal tissues. Radiation oncologists work side by side with professional dosimetrists, who apply filters and change the relative weights of the beams to meet their specifications. (One can think of dosimetrists' role as parallel to that of pharmacists in medical oncology.) They make sure the correct dose of therapy gets to where you prescribed it. In addition, physicists are also on hand to verify that the plan delivers its dose.

Days later (sooner in cases of oncologic-related emergencies like spinal cord compression or superior vena cava syndrome), the patient is on the treatment table, ready to be set up in the same position as at simulation. The therapist aims the collimator (the tube which shapes the beam of radiation as it exits) and takes an x-ray (port film). The port film images the patient's bony anatomy, ensuring that the field in the beam's actual pathway is the same as planned during simulation. If the radiation oncologist thinks there is any deviation, the therapist shifts the patient in the appropriate direction. Once optimized, treatment is given. As you can tell, medical students interested in radiation oncology must have a firm grasp of gross anatomy.

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